Multipackage module having stacked packages with asymmetrically arranged die and molding

ABSTRACT

Semiconductor chip packages have die asymmetrically arranged on the respective substrates. Two such packages having complementary arrangements can be stacked, one inverted with respect to the other, such that the two die are situated side-by-side in the space between the two substrates. Also, multipackage modules include stacked packages, each having the die asymmetrically arranged on the substrate. Adjacent stacked packages have complementary asymmetrical arrangements of the die, and one package is inverted with respect to the other in the stack, such that the two die are situated side-by-side in the space between the two substrates. Also, methods are disclosed for making the packages and for making the stacked package modules.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/670,443, filed Apr. 11, 2005, which is hereby incorporated byreference in its entirety.

BACKGROUND

This invention relates to semiconductor chip packaging and,particularly, to stacked package modules.

One approach to increasing the density of semiconductor functionality insemiconductor chip packages is to stack die, one over another, on apackage substrate. Electrical interconnection of the stacked die may bedie-to-die and/or die-to-substrate, for example by wire bonding. It istechnically difficult and therefore costly to test die prior to assemblyin the stacked die package, and some number of “bad” die are expected inthe supply. One bad die in a stacked die package can render the entirepackage bad and, accordingly, significant waste of materials andmanufacturing time can inevitably result in the manufacture of stackeddie packages, particularly where a larger number of die are stacked inthe package. Stacked die packages having as many as four, five or sixdie are in use. Stacked die packages can be made very thin, even wherespacers between adjacent die are required.

Another approach to increasing the density of semiconductorfunctionality in semiconductor chip packages is to stack packages, oneover the other, to form a stacked package module. Each package in themodule includes at least one die, affixed to and electricallyinterconnected with, a substrate. The packages in the stack areelectrically interconnected, for example by wire bonds between bondsites on the respective package substrates. This has the advantage thatthe packages can be fully tested before they are assembled in the stack;“bad” packages are discarded, and only packages testing as “good” areused in the module.

Several elements contribute to the thickness of a typical stackedpackage module. At a minimum, the thicknesses of the respectivesubstrates and die, and die attach adhesive, contribute. Additionally,where the die in each package are molded (or encapsulated) the mold caphas a thickness typically greater than that of the die, and where thedie is wire bonded to the substrate the mold cap must be thick enough tocompletely cover the wires, plus a tolerance for variation in wire loopheight. And typically the package stack is also molded or encapsulatedwith a module molding, which may add additional thickness.

In products where a limit is imposed on both package footprint andpackage thickness, such as for example in mobile devices such ascellular telephones, PDAs, digital cameras, and various consumerelectronic devices, it is desirable to make packages (or modules) asthin as possible without increasing the footprint beyond the limits.

SUMMARY

In one general aspect the invention features semiconductor chip packageshaving asymmetrically arranged die. Two such packages havingcomplementary arrangements can be stacked, one inverted with respect tothe other, such that the two die are situated side-by-side in the spacebetween the two substrates. In some embodiments the die is affixed toits respective substrate using an adhesive, and is electricallyinterconnected to the substrate by wire bonding; and in some embodimentsthe die is mounted onto the respective substrate by flip-chipinterconnection. The die may be molded.

In another general aspect the invention features multipackage modulesincluding stacked packages, each having asymmetrically arranged die. Thepackages have complementary asymmetrical arrangements, and one packageis inverted with respect to the other in the stack, such that the twodie are situated side-by-side in the space between the two substrates.The z-interconnection between adjacent packages is by solder balls, andthe solder ball height is sufficient to provide space for the die.Because the die are situated side-by side, the module thickness isreduced.

In another general aspect the invention features methods for making thepackages and for making the stacked package modules.

The stackable complementary packages according to the invention can bemade using currently available manufacturing equipment and materials andconventional surface mount technologies. The assembly process can beless complex than for modules having packages stacked one over theother, and the resulting thickness profile can be less. Stack thicknessin module assemblies is reduced according to the invention, by virtue ofthe fact that the two die on the two joined complementary packages sharethe space between the substrates and an additional die and die attachand mold cap thickness is avoided. Manufacturing costs can be reducedaccording to the invention by performing only a single solder ballreflow for the entire assembly, following alignment of the stackedcomplementary packages. The individual packages are fully testable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic sketch in a plan view showing a die mountedasymmetrically on a substrate according to a first embodiment of theinvention.

FIGS. 1B and 1C are diagrammatic sketches in side and front elevationalviews showing the die mounted asymmetrically on the substrate as in FIG.1A.

FIG. 2A is a diagrammatic sketch in a plan view as in FIG. 1A, in whichthe asymmetrically placed die has been molded according to an embodimentof the invention.

FIGS. 2B and 2C are diagrammatic sketches in side and front elevationalviews showing the molded asymmetrically mounted die on the substrate asin FIG. 2A.

FIG. 3A is a diagrammatic sketch in a plan view as in FIG. 2A, in whichz-interconnection solder balls have been mounted onto solderinterconnect pads on the substrate to complete a stackable packageaccording to a first embodiment of the invention.

FIGS. 3B and 3C are diagrammatic sketches in side and front elevationalviews showing the completed stackable package as in FIG. 3A.

FIG. 4A is a diagrammatic sketch in a plan view showing a die mountedasymmetrically on a substrate according to a second embodiment of theinvention.

FIGS. 4B and 4C are diagrammatic sketches in side and front elevationalviews showing the die mounted asymmetrically on the substrate as in FIG.4A.

FIG. 5A is a diagrammatic sketch in a plan view as in FIG. 4A, in whichthe asymmetrically placed die has been molded according to the secondembodiment of the invention.

FIGS. 5B and 5C are diagrammatic sketches in side and front elevationalviews showing the molded asymmetrically mounted die on the substrate asin FIG. 2A.

FIG. 6A is a diagrammatic sketch in a plan view as in FIG. 5A, in whichz-interconnection solder balls have been mounted onto solderinterconnect pads on the substrate to complete the stackable packageaccording to the second embodiment of the invention.

FIGS. 6B and 6C are diagrammatic sketches in side and front elevationalviews showing the completed stackable package as in FIG. 6A.

FIGS. 7A-9B are diagrammatic sketches in side and front elevationalviews showing steps in the construction of a stacked multipackagemodule, having two stacked packages, according to an embodiment of theinvention.

FIGS. 8A-12B are diagrammatic sketches in side and front elevationalviews showing steps in the construction of a stacked multipackagemodule, having four stacked packages, according to an embodiment of theinvention.

DETAILED DESCRIPTION

The invention will now be described in further detail by reference tothe drawings, which illustrate alternative embodiments of the invention.The drawings are diagrammatic, showing features of the invention andtheir relation to other features and structures, and are not made toscale. For improved clarity of presentation, in the FIGS. illustratingembodiments of the invention, elements corresponding to elements shownin other drawings are not all particularly renumbered, although they areall readily identifiable in all the FIGS. Also for clarity ofpresentation certain features are not shown if the FIGS., where notnecessary for an understanding of the invention. For example, thepatterned metal layers at the substrate surface are not shown, and theinterconnections (wires or bumps) of the die to the substrate are notshown.

According to one aspect of the invention, packages have the dieasymmetrically arranged on the substrate. That is, the die is attached(either affixed and wire bonded or mounted in a flip-chip fashion) on adie attach region toward an edge of the substrate, leaving an unoccupiedregion near the opposite edge of the substrate. In a firstconfiguration, interconnect solder balls are mounted on the die mountside of the substrate; and in a complementary second configuration,solder balls are mounted on the side of the substrate opposite the diemount side. Complementary pairs of packages are stacked, one invertedwith respect to the other, and the respective package substrates areelectrically interconnected by the solder balls on the package that hassolder balls on the die mount side of its substrate. The solder ballheight is great enough to provide a standoff between the substrates toaccommodate the thickness of the die (and die attach), and the packagesare oriented so that the die on the first package is situated in thespace between the package substrates over the unoccupied region of thesecond package substrate.

Turning now to FIGS. 1A, 1B and 1C there is shown a die 14 mountedasymmetrically on a die attach region 15 on a die mount surface 13 of asubstrate 12 according to the invention. The die attach region 15 issituated toward an edge of the substrate, leaving an unoccupied region16 of the die mount surface 13 situated toward the opposite edge of thesubstrate. The package substrate 12 is preferably a laminate substratehaving at least two patterned metal layers with dielectric layersbetween, that is, it includes at least a first “upper” patterned metallayer at the die mount surface 13, and a second “lower” patterned metallayer at the surface (the “land” side) 11 opposite the die mount side.The various metal layers are patterned to provide suitable tracecircuitry, and vias through the dielectric layers serve for connectionbetween the layers. A passivation layer over the upper and lowerpatterned metal layers is patterned with openings exposing sites on thetraces for electrical connection of the die, and exposing ball pads(shown at 17 in rows or arrays, at the die mount surface) for mountingsolder balls. The die may be affixed to the die attach region using adie attach adhesive (such as a die attach epoxy or film) with the activeside of the die facing away from the substrate, and electricallyinterconnected by wire bonds between die pads (not shown in the FIGS.)and bond pads on the substrate (not shown). Or, the die may be mountedonto the substrate by flip chip attachment (not shown) with the activeside of the die facing toward the substrate and electricallyinterconnected with bond sites on the substrate using conductive bumpsor balls.

The die can then be molded, as shown in FIGS. 2A, 2B, and 2C. Where thedie is interconnected by wire bonding, molding may be necessary, toprevent damage to the wires during subsequent steps. The molding 24covers the die and wire bonds (where wire bond interconnection is used),and is formed to have a substantially planar “upper” surface 25. Wherethe die is mounted by flip-chip interconnection, a molding may not berequired, although an underfill may be desirable, to fill the bumpstandoff space between the die and the substrate and to mechanicallystabilize the interconnection.

Then, as shown in FIGS. 3A, 3B, and 3C, z-interconnection solder balls37 are mounted on the ball pads on the die mount surface 13 of thesubstrate 12. Arrangements of ball pads and solder balls other thanillustrated in the FIGS. can be employed; in any event they are arrangedso as not to occlude the unoccupied region 16 of the die mount surface13 of the substrate. And they are arranged so that they provide a stablesupport for the complementary package to be inverted and mounted overthe first package. The solder balls are dimensioned such that, when thecomplementary packages are joined and the solder balls reflowed, theball height provides clearance between the adjacent substrates toaccommodate the die (and, where present, the molding). Mounting thesolder balls completes the first package 30, in which the solder ballsare mounted on the die mount side of the substrate. As may beappreciated, as the solder balls collapse during the reflow to join thetwo complementary packages, the upper surface 25 of the molding 24 maycontact the unoccupied region of the complementary package substrate,limiting further collapse of the solder balls.

A complementary package 60 according to an embodiment of the invention,in which the solder balls are mounted on the land side of the substrate,can be made as shown in FIGS. 4A-6C.

Turning now to FIGS. 4A, 4B and 4C there is shown a die 44 mountedasymmetrically on a die attach region 45 on a die mount surface 43 of asubstrate 42 according to the invention. The die attach region 45 issituated toward an edge of the substrate, leaving an unoccupied region46 of the die mount surface 43 situated toward the opposite edge of thesubstrate. The package substrate 42 is preferably a laminate substratehaving at least two patterned metal layers with dielectric layersbetween, that is, it includes at least a first “upper” patterned metallayer at the die mount surface 43, and a second “lower” patterned metallayer at the surface (the “land” side) 41 opposite the die mount side.The various metal layers are patterned to provide suitable tracecircuitry, and vias through the dielectric layers serve for connectionbetween the layers. A passivation layer over the upper and lowerpatterned metal layers is patterned with openings exposing sites on thetraces for electrical connection of the die, and exposing ball pads(shown at 47 in rows or arrays, at the die mount surface) for mountingsolder balls. The die may be affixed to the die attach region using adie attach adhesive (such as a die attach epoxy or film), andelectrically interconnected by wire bonds between die pads (not shown inthe FIGS.) and bond pads on the substrate (not shown). Or, the die maybe mounted onto and electrically interconnected with the substrate byflip chip attachment.

The die can then be molded, as shown in FIGS. 5A, 5B, and 5C. Where thedie is interconnected by wire bonding, molding may be necessary, toprevent damage to the wires during subsequent steps. The molding 54covers the die and wire bonds (where wire bond interconnection is used),and is formed to have a substantially planar “upper” surface 55. Wherethe die is mounted by flip-chip interconnection, a molding may not berequired, although an underfill may be desirable, to fill the bumpstandoff space between the die and the substrate and to mechanicallystabilize the interconnection.

Then, as shown in FIGS. 6A, 6B, and 6C, z-interconnection solder balls67 are mounted on the ball pads on the land surface 41 of the substrate42. Arrangements of ball pads and solder balls other than illustrated inthe FIGS. can be employed; in any event they are arranged so that theyprovide a stable support for mounting the assembly onto a mother board,or onto an additional assembly, or onto another support, as describedbelow. Mounting the solder balls completes the second package 60, inwhich the solder balls are mounted on the land side of the substrate.

Assembly of complementary packages into multipackage modules accordingto the invention is shown by way of example in FIGS. 7A-9B and in FIGS.10A-12B.

Formation of a unit of joined complementary packages 30 and 60 is shownby way of example in elevational views in FIGS. 7A-8B. In FIGS. 7A (sideelevation) and 7B (front elevation) a first package 30 is shown invertedwith respect to a second package 60, and aligned so that the solderballs 37 on the die mount side of the first package substrate 12 arealigned with the ball pads (not shown in this view) on the die mountside of the second package substrate 42, and so that the surface 25 ofthe mold cap on the first package 30 is aligned with the unoccupiedregion 46 of the die mount side of the second substrate 42 and thesurface 55 of the mold cap on the second package 60 is aligned with theunoccupied region 16 of the die mount side of the first package 30. Themanipulation of the packages can be done using conventional packageassembly equipment. For example, the second package 60 can be placed ona support, and the first package can be manipulated into the appropriateposition using a pick-and-place tool. Once aligned, the complementarypackages are brought together, as suggested by the broken arrows in theFIGS., until the solder balls on the first package 30 contact the padson the second package substrate 46. At this point the complementarypackage pair unit is complete. The unit can be heated to remelt thesolder balls 37 and make the electrical interconnection of the packagepair. The balls are shown collapsed following remelt in the unitassembly 80 in FIGS. 8A and 8B. Then the assembly can be encapsulated,as shown at 95 in FIGS. 9A and 9B to fill in the space between thesubstrates 12 and 42 around the die 25 and 55 and the solder balls 37.This completes a module 90 having two complementary packages. The modulehas an “upper” surface 91, and the solder balls on the second package,numbered 97 in FIGS. 9A and 9B, serve for electrical interconnection ofthe module 90 with a device in which it is employed, such as amotherboard, for example, in a mobile computing or communicationsproduct.

Complementary package pair units, such as unit 80 in FIGS. 8A and 8B,can be stacked to form modules having four or more packages. FIGS.10A-12B illustrate for example the construction of a module 120 bystacking two complementary package pair units 80, 80′ one over theother. In FIGS. 10A and 10B, complementary package pair units 80, 80′,constructed for example as described with reference to FIGS. 7A-8B, areshown aligned so that the interconnect solder balls 67′ on package unit80′ are aligned with the ball pads (not shown in this view) on the landside 11 of substrate 12 of package 30 of package unit 80. The units arebrought together, as suggested by the broken arrows, until the solderballs 67′ contact the pads. This forms a four-package assembly. Theassembly is heated to reflow the solder balls 67′ and make electricalinterconnection between the two units 80, 80′. The balls are showncollapsed following remelt in the four-package assembly 110 in FIGS. 11Aand 11B. Then the assembly can be encapsulated, as shown at 125 in FIGS.12A and 12B to fill in the space between the substrates around the dieand the solder balls. This completes a module 120 having twocomplementary packages. The module has an “upper” surface 121, and thesolder balls on the lowermost package, numbered 127 in FIGS. 11A and11B, serve for electrical interconnection of the module 120 with adevice in which it is employed, such as a motherboard, for example, in amobile computing are communications product. The solder remelt can beperformed for all the solder ball interconnections in a single remeltstep.

Other embodiments are within the scope of the invention. For example,although the respective die on the complementary packages areillustrated in the FIGS. as having about the same dimensions, therespective die may in other embodiments have different thicknesses orfootprints, particularly where the die have different functionalities.And, for example, although the respective substrates in thecomplementary packages are illustrated in the FIGS. as having the samelength and width, the respective substrates may in other embodimentshave different footprints. In any event, the unoccupied region of thedie mount side of each substrate must be sufficiently large, and must beconfigured, to accommodate the length and width of the surface of thedie or of the molding over the die in the complementary package.

The multipackage modules can be useful in any of a variety of electronicdevices, and they can be particularly useful in products where a highdevice density is desirable, and where there may be limited space withinthe product to accommodate the dimensions (footprint, thickness) of thedevice assemblies. Such products include, for example, portablecommunications devices such as cellular telephones and personal digitalassistants, laptop computers, digital cameras, and electronicentertainment products.

1. A complementary package pair unit, comprising: a first semiconductorchip package, comprising a first substrate having a die mount side and aland side, the die mount side including a die attach region and anunoccupied region, a first package die attached in the die attach regionof the die mount side of the first substrate, and firstz-interconnection solder balls mounted on ball pads on the die mountside of the first substrate; and a second semiconductor chip package,comprising a second substrate having a die mount side and a land side,the die mount side including a die attach region and an unoccupiedregion, a second package die attached in the die attach region of thedie mount side of the first substrate; wherein the first package isstacked on the second package, the die mount side of the first packagefacing the die mount side of the second package, wherein the die attachregion of the first package is aligned with the unoccupied region of thesecond package, and wherein the first z-interconnection solder balls onthe first package contact ball pads on the die mount side of the secondsubstrate.
 2. The complementary package pair unit of claim 1 wherein thez-interconnection solder balls are reflowed to form z-levelinterconnection between the ball pads on the die mount side of the firstsubstrate and the contact ball pads on the die mount side of the secondsubstrate.
 3. The complementary package pair unit of claim 2, furthercomprising second z-interconnection solder balls mounted on ball pads onthe land side of the second substrate.
 4. A multipackage modulecomprising the complementary package pair unit of claim 2 and a moduleencapsulation in the volume between the first and second packages.
 5. Amultipackage module, comprising: a first complementary package pair unitas recited in claim 3; and a second complementary package pair unit,comprising: a third semiconductor chip package, comprising a thirdsubstrate having a die mount side and a land side, the die mount sideincluding a die attach region and an unoccupied region, a third packagedie attached in the die attach region of the die mount side of the firstsubstrate, and third z-interconnection solder balls mounted on ball padson the die mount side of the first substrate; and a fourth semiconductorchip package, comprising a fourth substrate having a die mount side anda land side, the die mount side including a die attach region and anunoccupied region, a fourth package die attached in the die attachregion of the die mount side of the first substrate; wherein the thirdpackage is stacked on the fourth package, the die mount side of thethird package facing the die mount side of the fourth package, whereinthe die attach region of the third package is aligned with theunoccupied region of the fourth package, and wherein the thirdz-interconnection solder balls on the third package contact ball pads onthe die mount side of the fourth substrate; herein the firstcomplementary package pair unit is stacked on the second complementarypackage pair unit, and wherein the second z-interconnection solder ballson the second package contact ball pads on the land side of the thirdpackage substrate.
 6. The multipackage module of claim 5, furthercomprising a module encapsulation in the volume between the first andsecond packages.
 7. The multipackage module of claim 6, furthercomprising a module encapsulation in the volume between the third andfourth packages.
 8. The multipackage module of claim 7, furthercomprising a module encapsulation in the volume between the second andthird packages.
 9. A method for making a multipackage module,comprising: making first and second semiconductor chip packages, eachaccording to the method recited in claim 1; mounting firstz-interconnect solder balls on ball pads on the first side of the firstpackage substrate; positioning the first and second packages in relationto one another such that the first side of each package substrate facestoward the first side of the other package substrate, and such that thedie attach region of each package substrate is aligned with theunoccupied region of the other package substrate; contacting the firstz-interconnect solder balls with ball pads on the first side of thesecond package substrate; and reflowing the first z-interconnect solderballs to effect electrical connection with ball pads on the first sideof the second package substrate.
 10. The method of claim 9, furthercomprising forming a module encapsulation between the packages.
 11. Themethod of claim 9, further comprising mounting second z-interconnectsolder balls on the second side of the second package substrate.
 12. Amethod for making a multipackage module, comprising providing first andsecond packages, each as recited in claim 1; mounting firstz-interconnect solder balls on ball pads on the first side of the firstpackage substrate; stacking the first package upon the second package,with the die mount sides of the packages facing one another and with thedie attach region of each package aligned with the unoccupied region ofthe other package substrate; and reflowing the first z-interconnectsolder balls to effect electrical connection with ball pads on the firstside of the second package substrate.
 13. The method of claim 12,further comprising forming a module encapsulation between the packages.14. The method of claim 12, further comprising mounting secondz-interconnect solder balls on the second side of the second packagesubstrate.
 15. An electronic device, comprising a multipackage moduleaccording to claim 5, electrically connected to underlying circuitry inthe device.